Lamotrigine — DFSRH MCQ

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EasyLamotrigineDFSRH

A 33-year-old woman with focal epilepsy takes lamotrigine 300 mg daily as monotherapy. She has been seizure-free for 3 years and takes no valproate or enzyme-inducing medication. She has regular heavy menstrual bleeding that restricts her activities, but assessment has identified no structural uterine pathology. She requests highly effective reversible contraception for at least 5 years and would prefer substantially lighter bleeding. She does not wish to rely on additional condom use to maintain contraceptive effectiveness. Pregnancy is reasonably excluded, and she is medically eligible for each method listed. Which is the most appropriate contraceptive method?

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Correct answer: D — A 52 mg levonorgestrel intrauterine device

Explanation lettering: B = shown as A · C = shown as B · D = shown as C · E = shown as D · A = shown as E

A 52 mg levonorgestrel intrauterine device is the best fit for both priorities. FSRH advises that its contraceptive effectiveness is not expected to be affected by lamotrigine, and it provides highly effective long-acting contraception without requiring additional condoms. It is also effective for heavy menstrual bleeding and is recommended as first-line treatment when there is no identified uterine pathology. A is less suitable because ethinylestradiol induces lamotrigine glucuronidation, substantially reducing lamotrigine exposure and potentially compromising seizure control. Continuous use avoids hormone-free-interval fluctuations but does not prevent the reduction during active treatment; lamotrigine may also modestly reduce progestogen exposure. B avoids oestrogen, but evidence concerning progestogen-only contraception is limited. FSRH advises vigilance for lamotrigine toxicity when a progestogen-only method is started and, because lamotrigine might reduce pill effectiveness, recommends additional reliable condom use as a precaution. C is long acting, but lamotrigine might reduce implant effectiveness; FSRH similarly advises additional condoms. It also does not predictably treat heavy menstrual bleeding. D is highly effective and unaffected by lamotrigine, making it a plausible alternative where non-hormonal contraception is prioritised. However, copper devices can increase menstrual blood loss and therefore conflict with her stated therapeutic objective.

Reference: Drug Interactions with Hormonal Contraception (May 2022) — https://www.fsrh.org/Common/Uploaded%20files/documents/drug-interactions-with-hormonal-contraception-5may2022.pdf FSRH Guideline: Intrauterine Contraception (March 2023, amended January 2025) — https://www.fsrh.org/Common/Uploaded%20files/documents/fsrh-clinical-guideline-intrauterine-contraception-mar-23-amended.pdf Heavy menstrual bleeding: assessment and management (NG88) (Published 14 March 2018; updated 24 May 2021) — https://www.nice.org.uk/guidance/ng88/chapter/Recommendations